Natural gas feedstocks from various parts of the world have differing nitrogen content. Reforming natural gas to provide hydrogen-rich reformate gas for use, for instance, in a fuel cell power plant must be done with relative efficiency. A relatively inexpensive and effective catalyst for converting the hydrocarbons in natural gas to a hydrogen-rich reformate gas is nickel. However, the nickel catalysts promote an undesirable side reaction, combining product hydrogen with nitrogen present in the natural gas, to form ammonia: 0.5 N2+1.5 H2=NH3. The ammonia reacts with both phosphoric acid fuel cells and proton exchange membrane fuel cells to cause significant decay in fuel cell performance. The problem is sufficiently serious to require the use of ammonia scrubbers between the reformer and the fuel cell power plant, in some cases.
While rhodium will promote production of hydrogen-rich reformate without producing any ammonia, the cost of rhodium is excessive, being many thousands of US dollars per ounce at this writing.